J. Scheuer et M. Orenstein, Optical vortices crystals: Spontaneous generation in nonlinear semiconductor microcavities, SCIENCE, 285(5425), 1999, pp. 230-233
Broad-area, vertical-cavity surface-emitting lasers were shown to switch th
eir emission mode from the regular single or multilobed Light fields to exh
ibit complex arrays of "dark beams." Examination of these dark spot arrays
revealed that they consist of multiple, closely packed optical vortices: op
tical fields that have phase singularities and show increased complexity as
the injection current Level is raised. Contrary to their complex appearanc
e, most of these Light distributions are not the result of a multimode (mul
tiple-frequency) operation but exhibit single-frequency characteristics. Th
e dark beam patterns can be described as emanating from a spontaneous proce
ss of transverse mode Locking of nearly degenerate modes, assisted by the L
aser nonlinearity. Surprisingly, these patterns show high resemblance to pa
tterns generated in other nonlinear scenarios that are completely different
both in scale and in mechanism.